1. Field of the Invention
The present invention relates in general to valve operating mechanisms of internal combustion engines, and more particularly to the valve operating mechanisms of a type having an improved lubricating oil supply arrangement that provides mutually contacting portions of moving parts with a sufficient lubricating oil.
2. Description of the Related Art
In order to clarify the task of the present invention, one conventional valve operating mechanism of an internal combustion engine will be briefly described before describing the detail of the present invention. The valve operating mechanism is disclosed in P2003-500602A (WO00/073635).
The valve operating mechanism of the publication is of a so-called “desmodromic cam driven variable valve (VVT)” type which comprises generally a camshaft that is driven by a crankshaft, valve opening and closing cams that are mounted on the camshaft and a control member that is positioned apart from the camshaft and has a supporting shaft. A rocker arm is swingably disposed on the supporting shaft and includes first and second arm portions that extend radially outward. The first arm portion is equipped at a middle part thereof with a first roller that contacts the valve opening cam and the second arm portion is equipped at a leading end thereof with a second roller that contacts the valve closing cam. Due to employment of the arrangement wherein the contact of the first roller with the valve opening cam and the contact of the second roller with the valve closing cam are constantly kept, swing movement of the rocker arm is actively carried out. Thus, in the desmodromic cam driven variable valve mechanism, there is no need of using a return spring that is usually employed in a conventional cam driven variable valve mechanism for enforcedly returning the rocker arm to a valve closing position.
To the camshaft, there are rotatably disposed a pair of swing cams that carry out an open/close movement of two intake valves through respective swing arms. Each swing arm has one end supported by a pivot member and the other end to which an end of a valve stem contacts.